Anion‐directed assemblies of europium(III) coordination polymers based on 1H‐benzimidazole‐5,6‐dicarboxylate: structures and luminescence properties

Two europium(III) coordination polymers (CPs), namely, polydiaquabis(μ₄‐1H‐benzimidazole‐5,6‐dicarboxylato‐κ⁶N³:O⁵,O^5′:O⁵,O⁶:O^6′)(μ₂‐oxalato‐κ⁴O¹,O²:O^1′,O^2′)dieuropium(III)] dihydrate], {Eu₂(C₉H₄N₂O₄)₂(C₂O₄)(H₂O)₂]·2H₂O}_n ( 1 ), and poly(μ₃‐1H‐benzimidazol‐3‐ium‐5,6‐dicarboxylato‐κ⁵O⁵:O^5′,O⁶:O⁶,O^6′)(μ₃‐sulfato‐κ³O:O′:O′′)europium(III)], Eu(C₉H₅N₂O₄)(SO₄)]_n ( 2 ), have been synthesized via the hydrothermal method and structurally characterized. CP 1 shows a three‐dimensional network, in which the oxalate ligand acts as a pillar, while CP 2 has a two‐dimensional network based on a europium(III)–sulfate skeleton, further extended into a three‐dimensional framework by hydrogen‐bonding interactions. The structural diversity in the two compounds can be attributed to the different acidification abilities and geometries of the anionic ligands. The luminescence properties of 1 display the characteristic europium red emission with CIE chromaticity coordinates (2/3, 0.34). Interestingly, CP 2 shows the characteristic red emission with CIE chromaticity coordinates (0.60, 0.34) when excited at 280 nm and a near‐white emission with CIE chromaticity coordinates (0.38, 0.29) when excited at 340 nm.